Reservoir performance expectations were exceeded at the Costayaco field in Colombia. Costayaco 1P reserves increased to 19.7 million barrels of oil ("MMBO") NAR at year-end 2012 from 16.4 MMBO NAR at year-end 2011 despite total production of 3.8 MMBO NAR before inventory adjustments in 2012;

Appraisal drilling in the Moqueta field in Colombia resulted in 1P reserves increasing 45% to approximately 8.7 MMBO, 2P reserves increasing 54% to 14.9 MMBO and 3P reserves increasing 108% to 26.9 MMBO on a company interest basis, and 1P reserves increasing to approximately 6.8 MMBO, 2P reserves increasing to 11.2 MMBO and 3P reserves increasing to 19.4 MMBO on a NAR basis. The limits of the field have not yet been defined;

Gran Tierra Energy produced approximately 8.4 MMBO of working interest oil before royalties and inventory adjustments or 6.4 MMBO NAR before inventory adjustments and 1.7 billion cubic feet ("Bcf") of company interest gas before royalties or 1.5 Bcf NAR in 2012;

Based on Gran Tierra Energy's 2012 year-end SEC company interest reserves and Gran Tierra Energy's 2012 total working interest production, Gran Tierra Energy's 1P, 2P, and 3P reserves life indices are 6.4 years, 8.9 years, and 13.6 years respectively.

Annual production for 2012 averaged a record of approximately 23,600company interest barrels of oil equivalent per day ("BOEPD") before royalties, or 18,000 BOEPD NAR, both before inventory adjustments. Production in the fourth quarter of 2012 increased to approximately 18,600 BOEPD NAR before inventory adjustments. Production for the month of January 2013, before inventory adjustments, increased further to average approximately 21,000 BOEPD NAR.

All reserves values contained in the 2012 Highlights provided above have been calculated using SEC rules. For reserves values calculated in compliance with Canadian National Instrument 51-101 - Standards of Disclosure for Oil and Gas Activities ("NI 51-101") and the Canadian Oil and Gas Evaluation Handbook ("COGEH"), see "Reserves Reported in Accordance with Canadian Reporting Requirements" below in this press release.

* Before royalties and inventory adjustments

"Through continued strong reservoir management, appraisal drilling and exploration success, Gran Tierra Energy had another outstanding year in growing reserves and production to record levels from our projects in Colombia, Brazil and Argentina. The company has been successful at consistently growing land, reserves and production over the past 8 years and is focused on continuing to add value for our shareholders through successful exploration and development drilling in the future," said Dana Coffield, President and CEO. "In 2012, we produced a record volume of oil, in spite of unexpected challenges posed by substantial transportation downtime due to pipeline disruptions on the OTA pipeline in Colombia. Our team has worked vigorously to put into place alternative transportation measures to mitigate possible future downtime impacts to crude transportation. These measures are now in place and operational. As a result, even with recent disruptions, the company achieved near record levels of production, before inventory adjustments, in January of this year."

"In 2013, we are focused on continuing to grow reserves through continued appraisal drilling in the Moqueta and Ramiriqui oil discoveries, and additional exploration drilling in Colombia, testing new oil resource play concepts in Brazil and Argentina, and evaluating a very high-impact oil exploration target at the recently drilled Bretaña Norte well in Peru. Gran Tierra Energy's 2013 capital budget is expected to be funded through available cash on hand, cash flow from operations and with potential periodic draws on our credit facility at current commodity prices and production levels," concluded Coffield.

Reserves Reported in Accordance with United States Reporting Requirements

The following reserves are reported consistent with United States Securities and Exchange Commission rules.

Total Company

The following two tables summarize Gran Tierra Energy's year-end 2012 company interest reserves and NAR reserves (calculated using average start-of-month 2012 oil prices). Also shown in the following table are Gran Tierra Energy's NAR reserves for year-end 2011 (calculated using average start-of-month 2011 oil prices).

Total Company

Light and Medium Oil and Liquids

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MBO **

MBO

MBO

Proved

Developed Producing

35,644

26,817

21,317

Developed Nonproducing

778

666

1,554

Undeveloped

14,280

11,011

8,051

Total Proved

50,702

38,494

30,922

Total Probable

19,641

14,784

10,489

Total Proved plus Probable

70,343

53,278

41,411

Total Possible

28,418

21,456

17,626

Total PPP

98,761

74,734

59,037

**MBO (thousand barrels of oil).

Total Company

Gas

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MMSCF***

MMSCF

MMSCF

Proved

Developed Producing

11,572

10,515

16,968

Developed Nonproducing

1,014

813

310

Undeveloped

1,624

1,448

1,044

Total Proved

14,210

12,776

18,322

Total Probable

6,087

5,136

25,716

Total Proved plus Probable

20,297

17,912

44,038

Total Possible

59,375

51,667

116,509

Total PPP

79,672

69,579

160,547

***MMSCF (million standard cubic feet)

Total Company

BOE

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

BOE****

BOE

BOE

Proved

Developed Producing

37,572

28,569

24,145

Developed Nonproducing

947

802

1,606

Undeveloped

14,551

11,252

8,225

Total Proved

53,070

40,623

33,976

Total Probable

20,656

15,640

14,775

Total Proved plus Probable

73,726

56,263

48,751

Total Possible

38,314

30,068

37,044

Total PPP

112,040

86,331

85,795

****BOE (barrel of oil equivalent).

1P, 2P and 3P reserves NAR (on an oil equivalent basis) increased largely due to positive technical adjustment to Costayaco reserves based on reservoir performance and additional appraisal drilling at Moqueta in Colombia.

Reserves were added through the Ramiriqui-1 exploration well in Colombia.

Reserves were added through development drilling in the Tiê field in the Recôncavo Basin, Brazil.

The Proa-2 development well on the Surubi Block, Argentina, successfully added reserves.

Partially offsetting reserve additions was 2012 full year production of 8.4 MMBO of company interest oil before royalties and 1.7 Bcf of company interest gas before royalties.

Colombia

Gran Tierra Energy's Colombia year-end 2012 company interest and NAR reserves are shown in the following two tables (calculated using average start-of-month 2012 oil prices). Also shown in the following two tables is Gran Tierra Energy's Colombian NAR reserves for year-end 2011 (calculated using average start-of-month 2011 oil prices).

Colombia

Light and Medium Oil and Liquids

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany InterestReserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

32,838

24,360

19,497

Developed Nonproducing

380

317

1,402

Undeveloped

8,989

6,432

4,526

Total Proved

42,207

31,109

25,425

Total Probable

15,178

10,915

5,913

Total Proved plus Probable

57,385

42,024

31,338

Total Possible

18,839

13,167

9,749

Total PPP

76,224

55,191

41,087

Colombia

Gas

(SEC Compliant)

2012 Year-End

Gran Tierra Energy Company Interest Reserves

2012 Year-End

Gran Tierra Energy NAR Reserves

2011 Year-End

Gran Tierra Energy NAR Reserves

Reserves Category

MMSCF

MMSCF

MMSCF

Proved

Developed Producing

8,370

7,757

13,927

Developed Nonproducing

993

794

0

Undeveloped

1,012

921

713

Total Proved

10,375

9,472

14,640

Total Probable

3,929

3,300

21,155

Total Proved plus Probable

14,304

12,772

35,795

Total Possible

5,353

4,239

72,026

Total PPP

19,657

17,011

107,821

The increase in 1P, 2P and 3P NAR oil reserves is mainly associated with positive technical adjustments in Costayaco reserves due to reservoir performance, additional development drilling in Costayaco, the appraisal drilling program in Moqueta field in Colombia, and the Ramiriqui-1 exploration well.

The Costayaco and Moqueta fields 2012 year-end NAR reserves are shown in the following two tables (calculated using average start-of-month 2012 oil prices). Also shown in the following two tables is a comparison of the Costayaco and Moqueta fields 2012 year-end gross lease reserves (calculated using average start-of-month 2012 oil prices) to the gross lease reserves estimated in December 31, 2011 (calculated using average start-of-month 2011 oil prices).

Approximately 3.8 MMBO NAR before inventory adjustments was produced from the Costayaco field in 2012. Through a successful field development and reservoir management program in 2012, Gran Tierra Energy was able to successfully mitigate reserve declines at the Costayaco field.

Gran Tierra Energy's Argentina company interest and NAR reserves are shown in the following two tables (calculated using average start-of-month 2012 oil prices). Also shown in the following two tables is Gran Tierra Energy's Argentina NAR reserves for year-end 2011 (calculated using average start-of-month 2011 oil prices).

Argentina

Light and Medium Oil and Liquids

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany InterestReserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

2,407

2,110

1,766

Developed Nonproducing

398

349

152

Undeveloped

3,868

3,335

3,226

Total Proved

6,673

5,794

5,144

Total Probable

2,929

2,530

3,389

Total Proved plus Probable

9,602

8,324

8,533

Total Possible

7,211

6,219

5,842

Total PPP

16,813

14,543

14,375

Argentina

Gas

(SEC Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MMSCF

MMSCF

MMSCF

Proved

Developed Producing

3,202

2,758

3,041

Developed Nonproducing

21

19

310

Undeveloped

612

527

331

Total Proved

3,835

3,304

3,682

Total Probable

2,158

1,836

4,561

Total Proved plus Probable

5,993

5,140

8,243

Total Possible

54,022

47,428

44,483

Total PPP

60,015

52,568

52,726

The 1P and 3P NAR liquid reserve additions are largely associated with positive adjustments at Puesto Morales and Surubi.

Brazil

Gran Tierra Energy's Brazil company interest and NAR reserves are shown in the following table (calculated using average start-of-month 2012 oil prices). Also shown in the following table is Gran Tierra Energy's Brazil NAR reserves for year-end 2011 (calculated using average start-of-month 2011 oil prices).

Brazil

Light and Medium Oil and Liquids

(SEC Compliant)

2012 Year-End

Gran Tierra Energy Company Interest Reserves

2012 Year-End

Gran Tierra Energy NAR Reserves

2011 Year-End

Gran Tierra Energy NAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

399

347

54

Developed Nonproducing

0

0

0

Undeveloped

1,423

1,244

299

Total Proved

1,822

1,591

353

Total Probable

1,534

1,339

1,187

Total Proved plus Probable

3,356

2,930

1,540

Total Possible

2,368

2,070

2,035

Total PPP

5,724

5,000

3,575

1P, 2P and 3P reserves were added through development drilling in Brazil and increasing working interest to 100% from 70% in Blocks REC-T-129, -142, -155 and -224 located in Brazil's Recôncavo Basin.

Reserves Reported in Accordance with Canadian Reporting Requirements

The following reserves estimates are compliant with NI 51-101 and COGEH (with forecasted oil price and costs):

Total Company

Total company

Light and Medium Oil and Liquids

(NI 51-101 compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

35,242

26,892

21,232

Developed Nonproducing

510

444

1,293

Undeveloped

13,996

10,920

8,448

Total Proved

49,748

38,256

30,973

Total Probable

19,528

15,006

10,601

Total Proved plus Probable

69,276

53,262

41,574

Total Possible

28,755

22,105

18,224

Total PPP

98,031

75,367

59,798

Total Company

Gas

(NI-51-101 Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MMSCF

MMSCF

MMSCF

Proved

Developed Producing

11,572

10,515

16,971

Developed Nonproducing

1,014

812

306

Undeveloped

1,483

1,327

1,045

Total Proved

14,069

12,654

18,322

Total Probable

6,480

5,550

25,721

Total Proved plus Probable

20,549

18,204

44,043

Total Possible

59,086

51,529

116,519

Total PPP

79,635

69,733

160,562

Total Company

BOE

(NI-51-101 Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

BOE

BOE

BOE

Proved

Developed Producing

37,171

28,645

24,061

Developed Nonproducing

679

579

1,344

Undeveloped

14,243

11,141

8,622

Total Proved

52,093

40,365

34,027

Total Probable

20,608

15,931

14,888

Total Proved plus Probable

72,701

56,296

48,915

Total Possible

38,603

30,693

37,644

Total PPP

111,304

86,989

86,558

Colombia

Gran Tierra Energy's year-end 2012 Colombia company interest and NAR liquid reserves are shown in the following table (NI 51-101 compliant with forecast oil price and cost). Also shown in the following table are Gran Tierra Energy's Colombian NAR reserves for year-end 2011 (NI 51-101 compliant with forecast oil price and cost).

Colombia

Light and Medium Oil and Liquids

(NI 51-101 compliant)

2012 Year-End

Gran Tierra EnergyCompany InterestReserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

32,437

24,436

19,373

Developed Nonproducing

112

96

1,141

Undeveloped

8,805

6,427

4,934

Total Proved

41,354

30,959

25,448

Total Probable

14,966

11,055

6,029

Total Proved plus Probable

56,320

42,014

31,477

Total Possible

19,175

13,820

10,196

Total PPP

75,495

55,834

41,673

Gran Tierra Energy's year-end 2012 Colombia company interest and NAR gas reserves are shown in the following table (NI 51-101 compliant with forecast gas price and cost). Also shown in the following table are Gran Tierra Energy's Colombian NAR reserves for year-end 2011 (NI 51-101 compliant with forecast gas price and cost).

Colombia

Gas

(NI-51-101 Compliant)

2012 Year-End

Gran Tierra EnergyCompany Interest Reserves

2012 Year-End

Gran Tierra EnergyNAR Reserves

2011 Year-End

Gran Tierra EnergyNAR Reserves

Reserves Category

MMSCF

MMSCF

MMSCF

Proved

Developed Producing

8,371

7,757

13,926

Developed Nonproducing

993

794

0

Undeveloped

980

892

714

Total Proved

10,344

9,443

14,640

Total Probable

4,213

3,621

21,156

Total Proved plus Probable

14,557

13,064

35,796

Total Possible

5,063

4,102

72,026

Total PPP

19,620

17,166

107,822

The Costayaco and Moqueta fields 2012 year-end NAR reserves are shown in the following two tables (with forecast oil price and cost). Also shown in the following two tables is a comparison of the Costayaco and Moqueta fields 2012 year-end gross lease reserves (with forecast oil price and cost) to the gross lease reserves estimated at December 31, 2011 (with forecast oil price and cost).

Costayaco

Light and Medium Oil

(NI 51-101 compliant)

2012 Year-End

Costayaco Gran Tierra Energy NAR Reserves

2012 Year-End

Costayaco Gross Lease Reserves

2011 Year-End

Costayaco GrossLease Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

17,415

24,535

19,855

Total Proved

19,929

28,139

23,216

Total Probable

3,572

5,067

2,496

Total Proved plus Probable

23,501

33,206

25,712

Total Possible

2,655

3,799

7,836

Total PPP

26,156

37,005

33,548

Moqueta

Light and Medium Oil

(NI 51-101 compliant)

2012 Year-End

Moqueta NAR Reserves

2012 Year-End

Moqueta Gross Lease Reserves

2011 Year-End

Moqueta Gross Lease Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

3,709

4,190

2,137

Total Proved

6,794

8,478

5,973

Total Probable

4,586

6,457

3,727

Total Proved plus Probable

11,380

14,935

9,700

Total Possible

8,501

11,922

3,243

Total PPP

19,881

26,857

12,943

Argentina

Gran Tierra Energy's Argentina year-end 2012 company interest and NAR liquid reserves are shown in the following table (NI 51-101 compliant with forecast oil price and cost). Also shown in the following table is Gran Tierra Energy's Argentina NAR reserves for year-end 2011 (NI 51-101 compliant with forecast oil price and cost).

Argentina

Light and Medium Oil and Liquids

(NI 51-101 compliant)

2012 Year-End

Gran Tierra Energy Company Interest Reserves

2012 Year-End

Gran Tierra Energy NAR Reserves

2011 Year-End

Gran Tierra Energy NAR Reserves

Reserves Category

MBO

MBO

MBO

Proved

Developed Producing

2,406

2,109

1,803

Developed Nonproducing

398

348

152

Undeveloped

3,768

3,251

3,226

Total Proved

6,572

5,708

5,181

Total Probable

3,028

2,615

3,420

Total Proved plus Probable

9,600

8,323

8,601

Total Possible

7,212

6,220

5,977

Total PPP

16,812

14,543

14,578

Gran Tierra Energy's Argentina year-end 2012 company interest and NAR gas reserves are shown in the following table (NI 51-101 compliant with forecast oil price and cost). Also shown in the following table is Gran Tierra Energy's Argentina NAR reserves for year-end 2011 (NI 51-101 compliant with forecast oil price and cost).

Gran Tierra Energy Inc. is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated in the United States, trading on the NYSE MKT Exchange (GTE) and the Toronto Stock Exchange (GTE), and operating in South America. Gran Tierra Energy holds interests in producing and prospective properties in Argentina, Colombia, Peru and Brazil. Gran Tierra Energy has a strategy that focuses on establishing a portfolio of producing properties, plus production enhancement and exploration opportunities to provide a base for future growth.

Possible reserves are those additional reserves that are less certain to be recovered than Probable reserves. There is a 10% probability that the quantities actually recovered will equal or exceed the sum of Proved plus Probable plus Possible reserves. The estimate of reserves for individual properties may not reflect the same confidence level as estimates of reserves for all properties, due to the effects of aggregation. A BOE is calculated using the conversion factor of six thousand cubic feet ("Mcf") of natural gas being equivalent to one barrel of oil. BOEs may be misleading, particularly if used in isolation. A BOE conversion ratio of 6 Mcf : 1 barrel of oil is based on an energy equivalency conversion method primarily applicable at the burner tip and does not represent a value equivalency at the wellhead.

Forward-Looking Statements

The statements in this press release regarding Gran Tierra Energy's expectations, plans, projections and actions including, reserve life index, Gran Tierra Energy's expectations regarding its 2013 exploration and development drilling campaign, reservoir management and production, and expected funding of Gran Tierra Energy's 2013 capital program are "forward-looking statements" within the meaning of the U.S. federal and Canadian securities laws, including Canadian Securities Administrators' National Instrument 51-102 - Continuous Disclosure Obligations and the U.S. Private Securities Litigation Reform Act of 1995. Statements containing the words "estimates", "expects", "continue", "will", "may", "grow", "anticipated" and variations of these words are forward-looking statements.

The forward-looking statements contained in this news release reflect several material factors and expectations and assumptions of Gran Tierra Energy including, without limitation, assumptions relating to the accuracy of its reserves estimates, the continuity of certain industry conditions, the ability of Gran Tierra Energy to execute its current business and operational plans in the manner currently planned. Although Gran Tierra Energy believes that the assumptions underlying, and expectations reflected in, these forward-looking statements are reasonable, it can give no assurance that these assumptions and expectations will prove to be correct.

The forward-looking statements contained in this press release are subject to risks, uncertainties and other factors that could cause actual results or outcomes to differ materially from those contemplated by the forward-looking statements. Factors that could cause results to differ materially from those described in the forward-looking statements include: Gran Tierra Energy's operations are located in South America, and unexpected problems can arise due to guerilla activity, technical difficulties and operational difficulties which impact the production, transportation or sale of oil and gas; changing prices for crude oil may cause some scheduled projects or actions to become uneconomical, or may change Gran Tierra Energy's focus to other projects or actions which could be of more benefit to Gran Tierra Energy, which could cause projects or actions currently contemplated to be postponed or cancelled; unexpected problems due to technical difficulties, operational difficulties, and weather conditions; risks associated with not being able to fund the 2013 capital program through cash flow and cash on hand; and those other risks found in the periodic reports filed by Gran Tierra Energy with the SEC, including in the section entitled "Risk Factors" in its Quarterly Report on Form 10-Q filed with the SEC on November 7, 2012, and available at the SEC's internet site www.sec.gov and on SEDAR at www.sedar.com.

All forward-looking statements in this press release are expressly qualified by information contained in Gran Tierra Energy's filings with regulatory authorities and, subject to its obligations under applicable securities laws, Gran Tierra Energy does not undertake to publicly update forward-looking statements, whether as a result of new information, future events or otherwise.